1. Field of the Invention
The invention relates to a process for nonpolluting mass deacidification of all types of books and other printing and paper products, such as, magazines, records, etc., as well as to a device for performing these processes.
2. Background Art
The aging occurring in all printing and paper products and also especially in books during storing leads above all to a progressive deterioration of the paper substances by traces of acids released in the paper. If no countermeasures are taken, after some decades, this deterioration results in a complete disintegration of the papers.
Therefore, to preserve archives and library holdings of several hundred million books worldwide, it is necessary to neutralize the acids in paper and to simultaneously incorporate in the paper a sufficient amount of a substance that also neutralizes a future acid release in the paper.
In view of the very large amounts of books involved, only those processes are suitable for this purpose that permit treatment of the whole books, i.e., processes in which it is not necessary to open the bookbinding and to treat the pages individually. The same also applies to all kinds of archival holdings to be preserved, which also require the treatment of bound or otherwise assembled paper pages.
A known process consists in the treatment of books with vapors from metal alkyls, especially with vapors from diethylzinc. Due to the moisture in the paper, the metal alkyls are converted into the oxides of the metals, e.g., into zinc oxide, that remains in the paper, and is a good neutralizing agent for free acids. The metal alkyls suitable for this purpose, however, are materials which self-ignite in air and which in handling represent a constant potential risk of fire and explosion and, therefore, require extreme care.
Corresponding to a further known process, after previously being dried, the books are treated with a solution of a magnesium organic compound, such as, methylmagnesium carbonate in a suitable solvent. Also, in this case, the magnesium compound is converted by moisture in the paper into magnesium oxide and magnesium carbonate, both of which are able to neutralize the acids. Alcohols, e.g., methanol, in mixture with chlorofluoro-hydrocarbons, such as, trichlorotrifluoroethane are especially suitable as solvents.
Besides the advantage of incombustibility and nontoxicity, fluoro- and fluorochloro-hydrocarbons also offer the advantage of good compatibility with most book materials, such as, paper, cardboard, printing inks, glue and other adhesive agents, and are therefore especially well suited for this purpose.
Besides the high price, it is a special drawback that the named materials when they leak into the atmosphere, constitute considerable pollution and are a threat to the environment. Therefore, relevant laws for the handling of these materials require their substantial recovery and a very substantial purification of the exhaust air that is discharged from the treatment units.
Also, in the case of the treatment of books and other printed products, it follows from the above that after their treatment they have to be dried carefully so that they contain practically no solvent, and that the solvent-containing exhaust air from the drying process has to be purified except for very small residual contents of the solvents used.
While the drying of solvent-containing bulk goods normally causes no problems, the drying of compact, bound paper thus far has required very long drying periods. It is known, in fact, that the drying of books can be effectively supported by lowering the ambient pressure, but the reduced pressure simultaneously impedes the supply of the heat required for solvent evaporation.
It is further known, with drying under reduced pressure, i.e., vacuum drying, to introduce the evaporation heat to the substance to be dried by heat radiation. In books, this process, however, is applicable only with very small heat output since otherwise the books and especially the book-gluing are damaged.